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Humoral regulation of sleep closely related to homeostatic regulation something is being accumulated or used up sleep can be easily disturbed, but difficult to induce, appropriate control is a main issue two approaches: –harmful effects of sleep deprivation stress is difficult to eliminate motivation to sleep is almost as strong as motivation to avoid pain - torture –isolation of sleep factors following sleep deprivation during natural or experimentally evoked sleep testing prospective signal molecules normally present in our body 16/30

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Transfer of natural sleep parabiotic animals: Matsumoto, 1972 – higher synchronity of NREM and REM sleep than between animals joined by their skin only de Andres, 1976 – transplantation of an additional head to dogs – independent sleep, 108 h survival Siamese twins – independent sleep is possible, but contradicting results exist Mukhametov, 1985-87 sleep in dolphins – the two hemispheres can sleep separately described in other animals as well: birds, whale, etc. – complete decussation of the visual pathway is a prerequisite 19/30